diff --git a/wfvm/autounattend.nix b/wfvm/autounattend.nix
index f79df37..6033b21 100644
--- a/wfvm/autounattend.nix
+++ b/wfvm/autounattend.nix
@@ -13,8 +13,8 @@
 , timeZone ? "UTC"
 , services ? {}
 , impureShellCommands ? []
+, driveLetter ? "D:"
 , efi ? true
-, driveLetter ? if efi then "E:" else "D:"
 , ...
 }: